@inproceedings{li2021empirical,
    title={Empirical Analysis of Unlabeled Entity Problem in Named Entity Recognition},
    author={Yangming Li and lemao liu and Shuming Shi},
    booktitle={International Conference on Learning Representations},
    year={2021},
    url={https://openreview.net/forum?id=5jRVa89sZk}
}